Nong Fa Lake or Nongphatom Lake ('Blue Lake') is a volcanic crater lake in the mountains of Sanxay District, Attapeu Province, southeastern Laos, in the Dong Ampham National Biodiversity Conservation Area, about 12 kilometres from the Vietnamese border.

[1] Lonely Planet describes it as "magical",[2] a beautiful volcanic lake, similar to but larger than Yeak Lorn in Cambodia's Ratanakiri Province.

During the Vietnam War it was used by the North Vietnamese as a rest stop for soldiers hurt on the Ho Chi Minh Trail,[3] as well as US pilots recorded it as a navigation point and called it "Dollar Lake" because it was round.

[4] The lake is shrouded in legend, and Laotians refrain from bathing in it because they believe it is inhabited by a giant snake-pig who will devour bathers.

The hill tribes in the area say that if you do swim in the waters you will have eternal youth.